ASUNCION, Paraguay— President Fernando Lugo fired Paraguay's military chiefs Wednesday, a day after denying he had worries about a coup amid calls for his impeachment.

In a statement given to journalists at the presidential palace, Lugo named new commanders for the army, air force and navy without explaining his reasons. The new chiefs will assume their posts Thursday, said the statement signed by the president.

There was no immediate reaction from the military or from the political opposition, which controls Congress.

The new military commanders must be approved by the Senate. Lugo did not immediately submit a formal request for their approval Wednesday, but he did schedule promotions and retirements for other military officers for Nov. 11, meaning more changes could happen soon.

The shuffling in the military command came only one day after Lugo, a left-leaning former Roman Catholic bishop, publicly dismissed speculation about a possible coup as he struggles with Congress over implementing economic and social changes.

"I can assure you as commander in chief of the armed forces that, institutionally, there is no danger of a military coup," he said Tuesday when asked about coup rumors. "There could be small military groups that are connected to or could be used by the political class, but institutionally, the military does not show any intent of reversing the process of democratic consolidation."

The rumors were apparently prompted by tanks seen headed from Paraguay's Brazilian border toward the capital. It turned out the tanks were simply returning after maintenance work in Brazil.

Lugo's firing of the military chiefs was announced only hours after U.S. Ambassador Liliane Ayalde delivered $1.4 million in equipment for a Paraguayan military anti-terror squad equipped with high-tech communications, weapons and night-vision gear and bulletproof vests.

"This ceremony shows once again that the United States remains completely committed to its close alliance with Paraguay and we will continue working with the government of Paraguay and President Lugo to advance the goals of professionalizing the Armed Forces," Ayalde said.

Since winning the presidency last year and ending 61 years of domination by the conservative Colorado Party, Lugo has been trying to push reforms that aim to benefit Paraguay's numerous poor.